I had to replace my cat today. The old one turned into a can of rocks.

I figured while I was at it, I may as well rip out the AIR crap. No emissions testing here, but I wanted to retain the cat due to the $25,000 fine.

Anyway, I had done a search and saw a few people stated that the size needed to plug the holes in the manifolds was 3/8" NPT. So I took out the #2 flare, stuck a square headed steel plug I had laying around in there to verify the size I needed. I wanted brass plugs and plus hex heads for ease of installation.

Well not knowing much about flare fittings I didn't bother measuring the plug I had used. I took the plug with me to Menards to find some like it, yet brass and with hex heads. I went straight to the plugs and grabbed the first 3/8" one and held the steel plug next to it. It was the same. So I grabbed 8 of them and left.

When I had got home, I grabbed one, screwed it in, and it fit. Good, right? So I continued to remove the rest of the tubes. I went to install #4 and the plug was too big. I started scratching my head thinking "WTF?".

I checked the rest of them compared to the one that was too big, and they were all too big. Well I then verified that the stock flare bolts were all the same size. So finally I pulled out the dial calipers and found that the steel plug, as well as the stock flares were 5/16" Wish I had done that the first time.

Obviously the morons who packaged these things put a 5/16" plug in a 3/8" baggie. Well of course this was at 7:40pm and Menards closed at 7pm.

Now the problem really begins. The only sizes that Menards had were 1/4" and 1/8" (I had paid attention to that, at least). So now what? Obviously I need 5/16", and obviously they make them, so where do I get them? Anyone know?

This really puts the truth in the statement that Jim85Iroc has in his sig. "Weekend projects aren't"

I guess my other question is, are some cars 3/8" and some 5/16"? Or did I just get a bum deal?

Thanx in advance for any replies,
AJ

 

I'm pretty sure mine were 1/2 pipe thread, i did it like a month ago I think I still have the bag I bought them in, I'll check when I get home

 

Well, I've never done it myself, but can offer this to you...

http://www.engineersedge.com/pipe_external_thrd.htm

Maybe it will help, maybe not. Just a concerned thirdgenner doing what I can.

 

Mine were 1/4" if I remember right.


Mark

 

A buddy of mine did that 'mod' at my house last year and I think he used 1/4" NPT..... Not 100% positive though......

 

I should have posted this after I found out. Sorry. I finished it Mon. night.

The good guys at NAPA set me straight. You guys are right. They are 1/4". But something I learned is that with flare fittings, they measure the nuts/plugs by the pipe that they're on, not the nut itself. So when you buy 1/4" flare fittings or plugs, the thread pattern is actually larger than that, but not given a size to use as a guide. And they are not NPT or "fine" or "course" threads. They have there own little secret cut. I guess so you only use flare nuts on flared pipes.

AJ